Holocaust generates concentrated powerful bio-nuclear microwave blasts of limited range. He usually focuses the blasts through the gun on his left arm. He also possesses vast superhuman strength, endurance, and invulnerability. He also has the ability to drain off the life force energy of a victim to increase his strength and fuel the shapeshifting and phasing properties of his crystalline armor. It is unknown what powers he gained and what powers he lost after becoming dependent on his armor. It's believed that he still possessed a certain degree of invulnerability before he gained the suit and it is possible he was completely invulnerable, as he was shocked when Scarlet Witch was able to injure him, and she makes impossible things possible. Although dependent on his armor for survival, he could continue to battle Exodus for some time after his armor was breached. Without his armor he would eventually dissipate.

Holocaust played a significant part in the Age of Apocalypse storyline as one of the Horsemen, a Biblically-inspired quartet of villains that enforced Apocalypse's cullings. He first appeared as an agent of his father Apocalypse in a human body. Spying on the X-Men's headquarters on Wundagore Mountain, he waited until most of the team left to attack. Scarlet Witch had been left in charge of the facility and the younger students at the school in case the team didn't come back alive. Holocaust, then calling himself Nemesis, fatally wounded Scarlet Witch and killed most of the young students. In revenge, Magneto destroyed his physical form, which was transported to his crystalline armor (both events happened off-panel), which was created by the Dark Beast.
The next time that he appeared he was in charge of the Infinites processing plant in Indianapolis. Sabretooth, having a vendetta against Holocaust, convinced Blink to teleport him and Wild Child after the villain. Rogue tried to object but Blink did as she was told. Sabretooth and Holocaust battled exhaustively, but eventually the villain got the upper hand. Chaining Sabretooth to a stone slab and slicing his chest, Holocaust left him for dead. Enraged by Sabretooth's apparent death, Blink attacked Holocaust and seemingly killed him in a vat of acid, but the villain emerged unharmed. The rest of the team came to the rescue and Rogue almost destroyed the villain, but he teleported away before it was too late. He returned to the citadel of his father, Apocalypse, where he encountered Nate Grey, also known as X-Man. Nate had no interest in fighting anyone other than Apocalypse, and quickly dispatched Holocaust with a massive psionic attack. However, Holocaust recovered soon afterward and again attacked Nate, leaving Magneto to fight Apocalypse alone. Holocaust and X-Man were evenly matched and fought for quite some time, until Nate used a piece of the M'Kraan Crystal to stab Holocaust in the stomach. The crystal, which is the nexus of all realities, had a unique effect on the two when combined with the energy that escaped from Holocaust's armor, transporting the pair into the main Marvel universe shortly before Bishop prevented the timeline from ever occurring... or so it seemed. An interesting side note to Holocaust is his lackey/ally called "Wolverine". This was not the same Wolverine from Earth 616 (who as called Weapon X in this reality) but rather an entirely new villain cloned from cells taken from the left hand of Weapon-X (which was cut off in the same fight in which Cyclops lost his left eye) .
Main Marvel Universe
Holocaust wound up floating in space, where his body was taken aboard Magneto's orbiting space station, Avalon. Former New Mutants member Rusty Collins was ordered to guard his body, which was thought to be frozen, and his life force was drained by the villain. Holocaust then went on a rampage, fighting Exodus and subsequently destroying the space station.
He became the main antagonist of X-Man, who also was transported to Earth-616, and they had several run-ins. In one such incident he was acting as the emissary of Onslaught. They battled until Holocaust's armor was broken and he had to flee, but he revealed that he was only sent to gauge X-Man's potential. Now that he had, Onslaught would come for him in person.
Exiles
Holocaust later became 'unhinged' in time and was forced to join the time-traveling group of heroes known as the Exiles, replacing the seemingly useless member Beak from the main Marvel universe. The roster at that time included Holocaust's enemies from the Age of Apocalypse's X-Men, Blink and Sabretooth, whom he had personal vendettas against. Finding himself back in his native reality, and with the knowledge that Apocalypse died--leaving him as rightful heir to his empire--Holocaust went off to claim his prize.
However he sensed the familiar energy of the M'Kraan Crystal and went to investigate. He found that the Army had confiscated the artifact from Apocalypse's citadel and had been trying to figure out what it was ever since. Holocaust also learned that there was another M'Kraan energy signature on the earth at that time--the Tallus. Holocaust agreed to work with the Exiles so they could confront the Timebroker and get back to their respective realities. Noting how the Dark Beast teleported inside of the crystal to be transported to a different reality, Holocaust deduced that they could do the same to reach the place where the Timebroker resided. Blink reluctantly agreed and the team found themselves at Panoptichron, the palace on the edge of reality that was the headquarters for the Timebroker--or more accurately the Timebreakers.
When the Exiles went to the Timebroker's base, they discovered a twisted, dictator-like version of Hyperion in charge. He had apparently died and had been placed inside of a crystal stasis wall by the Timebreakers, but he had recuperated and taken over the hub. Angry, Holocaust attacked Hyperion but proved to be no match for the supervillain, who broke open Holocaust's armor with a headbutt. He then inhaled Holocaust, leaving nothing left of Apocalypse's son but a broken shell.